Fixture for forming heating elements by hydraulic pressure

ABSTRACT

A fixture for forming heating elements of the dimpled plate type includes a flat piston plate carried on an inflatable bag for uniformly supporting an envelope made of metal sheets sealed together around their edges during inflation of the envelope. The envelope is positioned between two studded plates for restraining opposed portions of the sheets against separation as the envelope expands under internal hydraulic pressure. An upper portion of the fixture is mounted on a movable carriage so that the envelope can be placed in the fixture by loading from above.

United States Patent 1191 Fabri 14 1 June 5, 1973 154] FIXTURE FOR FORMING HEATING 3,410,202 11/1968 Chrubasik 1.72/63 ELEMENTS BY HYDRAULIC 3,512,239 5/1970 Rosenblad t..29/42l PRESSURE 2,908,238 10/1959 Bringwald ..72/57 [75] Inventor: Ernest S. Fabri, Willingboro, NJ. primary'gmmineruRichard Herbst [73] Assignee: Rosenblad Corporation, Princeton A ttorney-Lonmer P. Brooks, Alfred L. Haffner, Jr.

and Charles G. Mueller et a1.

22 Filed: Jan. 17,1972 [57] ABSTRACT A fixture for forming heating elements of the dimpled [21] Appl' 2l8429 plate type includes a flat piston plate carried on an inflatable bag for uniformly supporting an envelope [52] US. Cl ..72/57, 29/157.3 V, 29/202 D made of metal sheets sealed together around their [51] Int. Cl. ..B2ld 26/02 edges during inflation of the envelope. The envelope is [58] Field of Search ..29/157.3 B, 157.3 V, positioned between two studded plates for restraining 29/202 D; 113/1 C; 72/57, 58, 61 opposed portions of the sheets against separation as the envelope expands under internal hydraulic pres- [56] References Cited sure. An upper portion of the fixture is mounted on a movable carriage so that the envelope can be placed UNITED STATES PATENTS in the fixture by loading from above. 2,857,659 10/1958 Staples ..29/l57.3 V 9 Claims TDrawing Figures 26' i l l1. 1'' 111 {01k 0. V/// 5/ 4/ null PATENTEDJUN 5 I973 TE L.

FIXTURE FOR FORMING HEATING ELEMENTS BY HYDRAULIC PRESSURE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the formation of heat exchanger elements of the type in which channels for the flow of a heat exchange fluid are formed between a pair of opposed plates. More particularly the invention relates to a fixture or apparatus for use in the manufacture of such heat exchanger elements.

2. Description of the Prior Art U. S. Pat. No. 3,512,239 to Axel E. Rosenblad, issued May 19, 1970, discloses a method for forming dimpled plate heat exchanger elements by the use of hydrostatic pressure. That Rosenblad patent illustrates apparatus suitable for use in performing the method, but experience has shown that there are certain drawbacks in the use of such apparatus.

In the forming apparatus shown in U.S. Pat. No. 3,512,239, a pair of opposed plates are received between a rigid and an elastic support element. Since the elastic element comprises a metal diaphragm, the diaphragm must be very carefully designed and maintained to prevent its taking a permanent set which would make it impossible to remove a heating element after forming. Further, the apparatus of the prior patent does not permit top loading, and there is always a chance of misalignment and subsequent errors in forming when dies and heating element blanks are inserted into the apparatus. Loading requires care and is somewhat slow.

Prior to the above discussed Rosenblad patent plates for heat exchanger elements of the type described were individually formed by mechanical action in heavy, expensive presses using special dies. The separate plates then had to be carefully aligned and joined. The method of U.S. Pat. No. 3,512,239 represented a considerable advance in the art, but a better forming fixture was still desired.

SUMMARY OF THE INVENTION The fixture for forming heat exchanger elements according to this invention consists of a fixed bottom part and a top part movable as a carriage upon rails to overlie the bottom part after an envelope of flat plates sealed together at their periphery has been placed on the bottom part. The fixed bottom part includes an upward opening rectangular box in which there is an inflatable bag. A piston plate, lying on the inflatable bag, is movable in a vertical direction. The piston plate supports a lower studded plate having studs directed upwards.

The envelope to be expanded by hydraulic pressure rests on the studs of the plate and a symmetrically disposed upper studded plate with downwardly directed studs is positioned above the envelope. The movable top part on its carriage may be readily moved into position over the upper studded plate.

After the top part of the fixture has been moved into place, the envelope isexpanded by the introduction of fluid under pressure between its pair of plates. The plates separate from each other everywhere except at their edges and at those points where they are restrained by the studs.

The use of a flat piston plate according to the invention, carried on an inflatable bag, results in uniform distribution of pressure over the whole area of the heating element. The sliding top facilitates easy positioning of the envelope to be expanded into a heating element, as well as removal of the expanded element. Top loading saves a considerable amount of time. The fixture can be easily disassembled in the event that maintenance is required.

These and other features of the invention will be more fully understood from the following detailed description of a preferred embodiment of the invention, when taken in combination with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing: FIG. 1 is a side view of the structural frame and carriage arrangement for the fixture according to a preferred embodiment of the invention.

FIG. 2 is an end view of the arrangement shown in FIG. 1 and illustrating the top part of the fixture in working position.

FIG. 3 is a detail view in section of a portion of the fixture according to the invention before inflation of the inflatable bag.

FIG. 4 is a sectional detail view generally similar to that of FIG. 3, after the bag has been inflated, but before expansion of the envelope to form a heating element.

FIG. 5 is a sectional detail view similar to those of FIGS. 3 and 4 illustrating the relationships assumed after expansion of the envelope.

FIG. 6 is an overall view in perspective of an envelope from which a heating element may be formed by use of the fixture of the invention.

FIG. 7 is an overall view in perspective of a finished heating element, formed by using the fixture of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT A fixture according to the invention, generally indicated by the reference numeral 10, is shown in the side view of FIG. 1 of the drawing, and in the end view of FIG. 2. A fixed bottom part 11 of the fixture 10 is supported by a sturdy frame 12, which may suitably be of structural steel, with braced uprights 13 carrying a pair of elongated parrallel rails or tracks 14.

A carriage 15, comprising the upper part 16 of the fixture 10 has a plurality of trolley wheels 17 for motion along the rails 14, from a displaced position shown in dashed lines at the left in FIG. I to the operative position shown at the right in FIG. I. When the carriage 15 is at its operative position, the upper part 16 of the fixture 10 lies directly over the fixed bottom part 11 as best shown in FIG. 2.

The detail views of FIGS. 3-5 illustrate the cooperation of the elements of the fixture 10 in the formation of a heating element. The area represented by these views corresponds to that shown at the upper left in FIG. 2. The bottom part 11 of the fixture 10 has a generally rectangular ledge 20 extending horizontally along each of its sides 21 for guiding the sliding motion of the upper part 16 by cooperating with horizontal grooves 22 formed on the inner sides of downwardly extending side pieces 23 affixed to both sides of the top part or carriage 15. The grooves 22 are generally rectangular in profile and extend horizontally along the entire length of the side pieces 23.

The side pieces 23 may be suitably joined to the generally rectangular flat body 24 of the upper part 16 by a tongue and groove joint as shown at 25, positively secured by means of suitable screws 26 at spaced locations along the length of the top part 15. The side pieces 23 also receive bolts 27 which act as axles for trolley wheels 17. The trolley wheels 17 are preferably provided at spaced locations along the top part 16 for rolling motion on the tracks 14 at both sides of the carriage 15.

The body 241 of the top part 16 is heavily constructed to withstand pressures applied in formation of heating elements, and has a downward facing flat lower surface 30. The bottom part 11 of the fixture has a generally rectangular upstanding rim 31 around its entire periphery, surrounding an upwardly open box-like space 32 formed in the bottom part ill. The space 32 has a flat lower surface 33 and upstanding flat walls 34 formed by the inner sides 34 of the rim 31.

As shown in FIGS. 3-5, the space 32 contains an inflatable bag 35, which may be of rubber or other suitable material. The bag 35 is itself rectangular in plan and of a suitable size to cover the flat surface 33 of the space 32. FIG. 3 shows the bag 35 in the generally deflated state it assumes during loading of the fixture 10.

Directly above the bag 35, and resting thereon, is a flat rigid piston plate 36, which is rectangular in plan and slightly smaller than the bottom surface 33 of the space 32, for free motion up and down within the rim 31 upon inflation and deflation of the bag 35. In FIG. 3 the. piston plate 36 is shown in its lowered position. In this position the plate 36 lies entirely within the boxlike space 32, and its flat upper surface 37 is parallel to the lower surface of the upper part 15. The space between the surfaces 30 and 37 is sufficient for the reception of an envelope 40 to be expanded into a heating element and a pair of upper and lower studdedplates 41 and 42 which act as dies in the forming process in a manner to be described. The studded plates 41 and 42 may suitably be formed of aluminum.

The bag is inflatable by any suitable means, (not shown in the drawing). Such inflating means may. comprise an hydraulic pump communicating with the bag 35 at one end of the lower part 11, so that a connecting hose or the like does not interfere with the motion of 45 the upper part 16.

Reference is now made to FIG. 6, showing an envelope dti of the type which may be expanded into a heating element in accordance with the invention. The envelope 44B is composed of a pair of matching symmetrical sheet metal plates M and 45 welded together at their edges 46 as best seenin FIG. 5. The joint 46 between the plates 44 and 45 is tight, leak-proof and pressure proof and extends entirely around the envelope except at one location indicated at 47, where a nozzle 43 is provided for the introduction of water under pressure between the plates 44 and to expand portions of the plates away from each other in a manner to be described. A finished heating element is illustrated in FIG. '7.

Returning to FIGS. 3-5, the nature of the studded plates $11 and 42 can be understood in their relationship to the envelope 40. The upper and lower studded plates 611 and 62 may suitably be identical in form, so only the lower plate 42 will be described. The studded plate 42 is generally rectangular in plan, and of an area somewhat greater than the rectangular space 32 formed within the rim 31, so that the studded plate 42 overlies the rim 31 at all of its edges 48. Thus as shown in FIG. 3, the plate 42 may be placed in position above the bag 35 and piston studded plate 36 by centering the plate 42 over the piston plate 36. The plate 42 has a generally flat upper surface 49 from which a plurality of studs 50 extend upwardly at spaced locations in a desired pattern. Each stud 50 is smoothly rounded and has a flattened head 51 for contacting the envelope 40. The studs 5th may be circular in plan as in the illustrated embodiment or may take some other desired form such as elongated or oval in plan view, Reference is made to the aforementioned Rosenblad U.S. Pat. No. 3,512,239 for modified forms of studs. The studs 50 may be welded directly to the plate 42 or attached by some other suitable means.

The upper plate 41 has a matching array of studs 50a so that when the plate 41 has been positioned, a downwardly extending stud 50a presses against the envelope 40 at a position directly opposite each upwardly directed stud 50.

MODE OF OPERATION The use of the fixture 10 in the formation of heating elements as shown in FIG. 7 permits top loading and removal of the elements and exact positioning of the studs 50 and 50a. In a typical forming operation, the carriage 15 is rolled along the tracks 14 to the position shown at the left end of FIG. 1. This leaves the fixed bottom part 11 of the fixture 10 open for loading. The lower studded plate 42 may then be seated in position above the piston plate 36.

The next step is to place the envelope 40 atop the studs 50 of the lower studded plate 42 and to position the upper studded plate 41 above the envelope 40 with its studs 50a located symmetrically above the studs 50. This alignment is readily accomplished, since no structure obstructs view of the envelope 40 and plates 41, 42. By moving the carriage l5 toits operative position as shown in FIG. 1 and attaching the hydraulic pump, the fixture is readied for operation.

The inflatable bag 35, shown in its deflated state in FIG. 3, is then inflated. The piston plate 36 resting on the bag 35 begins moving upward as the bag is inflated. This upward motion in turn moves the studded plates 41, 42, and the envelope 40 held therebetween, upward until the upper studded plate 41 engages the surface 30 of the upper part 15, as shown in FIG. 4. The envelope 40 is completely flattened out at this point, even if some buckling had occured in welding together its two opposed plates 44 and 45. Comparison of FIGS. 3 and 4 will show how the ledge 20 is forced into abutment with the bottom of groove 22 to halt any further up ward motion or separation of the top-and bottom parts 15 and ll of the fixture 10. r The next step in the forming process is the expansion of the envelope 40 by the introduction of water under pressure through the nozzle 48. The introduction of water proceeds under pressure until an internal pressure slightly beyond the yield point of the envelope material is reached. The pressure in the inflated bag 35 must exceed the internal pressure in the envelope 40. Forming stainless steel elements with the plates 44 and 45 being 18 guage stainless steel has been found to require an internal pressure of about 500 pounds per square inch. In such a case. a suitable pressure for inflation of the bag35 is about 550 pounds per square inch.

This pressure will expand the envelope 40 to the contour shown in FIG. 5, with the plates 44 and 45 expanded away from each other everywhere except at their welded periphery 46 and at points held against expansion by the studs 50 and 50a. The use of pressure slightly beyond the yield point of the material causes the material to flow evenly around the stud heads 51.

The pressure on the expanded envelope 40 and the bag 35 is relieved after the envlope has reached the form shown in FIG. 6. The piston plate 36 then moves down to the position of FIG. 3. The top part 16 is then returned to its displaced position shown at the right in FIG. 1 leaving the studded plates 41 and 42 with the expanded element 40 therebetween uncovered. The heating element 40 and the plates 41 and 42 may then be removed from the fixture 10.

The expanded envelope 40 has assumed the shape shown in FIG. 7. The opposed dimples 60 of the plates 44 and 45 where the material was held against expansion may be spot welded together to provide the requisite strength for the heating element, which will have internal passages for fluid flow between the joined dimples 60. I

From the foregoing it will be understood that the fixture of the invention provides a means for simple and economical formation of dimpled plate heat exchanger elements. Numerous modifications and adaptations of the fixture of the invention will suggest themselves to those of ordinary skill in the art without departing from the spirit and scope of the invention.

What is claimed is:

l. A fixture for forming heat exchanger elements or the like of the type having opposed plates spaced by pairs of inward projections, comprising a fixed bottom fixture part and a top fixture part, means vertically spacing said bottom and top parts when said top part is in operative position, for reception of an envelope to be formed into a heat exchange element or the like, hydraulic piston means including an inflatable element carried by said bottom part for exerting upward pressure on said envelope, said top part including a carriage mounted for movement of said top part from an operative position overlying said piston means to a position horizontally displaced from said piston means.

2. The fixture of claim 1 wherein said bottom part includes an upwardly open space and said inflatable element is seated in said space.

3. The fixture of claim 3 wherein a flat piston plate, situated above said inflatable element, is mounted for vertical movement upon inflation of said inflatable element.

4. A fixture according to claim 1 wherein said envelope is formed by expansion through internal hydrostatic pressure, and including a pair of studded plates for receiving said envelope therebetween, one of said studded plates being positioned above said inflatable element and the other of said studded plates being positioned so that the studs thereof are opposed to the studs of said one studded plate.

5. A fixture according to claim 1 wherein said top part and said bottom part include elements providing spaced opposed flat surfaces when the top part is in its operative position for reception of die means and said envelope between said surfaces.

6. The fixture according to claim 1 wherein said inflatable element is an inflatable bag mounted in a space in said bottom part, and a flat rigid piston plate is mounted above said bag for upward movement upon inflation of said bag, lower die means positionable on said piston plate, upper die means positionable symmetrically above said lower die means for reception of said envelope between the die means for locally restraining said envelope against expansion, and means for applying internal hydrostatic pressure to said envelope for expanding the envelope.

7. A fixture according to claim 1 wherein said top and bottom parts include rigid flat plates for reception of and rigid support of upper and lower studded plates therebetween to form said heat exchanger elements or the like between said studded plates.

8. The fixture of claim .1 wherein said top and bottom parts are of substantially similar length and width.

9. The fixture of claim 1 wherein downwardly extending side portions of said top part are formed with longitudinal grooves for engagement of opposed ledges fromed on said bottom part to restrain said top part against vertical movement upon inflation of said inflatable member.

l I 4K 

1. A fixture for forming heat exchanger elements or the like of the type having opposed plates spaced by pairs of inward projections, comprising a fixed bottom fixture part and a top fixture part, means vertically spacing said bottom and top parts when said top part is in operative position, for reception of an envelope to be formed into a heat exchange element or the like, hydraulic piston means including an inflatable element carried by said bottom part for exerting upward pressure on said envelope, said top part including a carriage mounted for movement of said top part from an operative position overlying said piston means to a position horizontally displaced from said piston means.
 2. The fixture of claim 1 wherein said bottom part includes an upwardly open space and said inflatable element is seated in said space.
 3. The fixture of claim 3 wherein a flat piston plate, situated above said inflatable element, is mounted for vertical movement upon inflation of said inflatable element.
 4. A fixture according to claim 1 wherein said envelope is formed by expansion through internal hydrostatic pressure, and including a pair of studded plates for receiving said envelope therebetween, one of said studded plates being positioned above said inflatable element and the other of said studded plates being positioned so that the studs thereof are opposed to the studs of said one studded plate.
 5. A fixture according to claim 1 wherein said top part and said bottom part include elements providing spaced opposed flat surfaces when the top part is in its operative position for reception of die means and said envelope between said surfaces.
 6. The fixture according to claim 1 wherein said inflatable element is an inflatable bag mounted in a space in said bottom part, and a flat rigid piston plate is mounted above said bag for upward movement upon inflation of said bag, lower die means positionable on said piston plate, upper die means positionable symmetrically above said lower die means for reception of said envelope between the die means for locally restraining said envelope against expansion, and means for applying internal hydrostatic pressure to said envelope for expanding the envelope.
 7. A fixture according to claim 1 wherein said top and bottom parts include rigid flat plates for reception of and rigid support of upper and lower studded plates therebetween to form said heat exchanger elements or the like between said studded plates.
 8. The fixture of claim 1 wherein said top and bottom parts are of substantially similar length and width.
 9. The fixture of claim 1 wherein downwardly extending side portions of said top part are formed with longitudinal grooves for engagement of opposed ledges fromed on said bottom part to restrain said top part against vertical movement upon inflation of said inflatable member. 